Technical Field
The present invention relates to a strain of Bacillus sp.
The present invention also relates to biosurfactants produced by a strain of Bacillus sp and to uses thereof. It also relates to a composition comprising these biosurfactants, as well as a method for producing these biosurfactants.
The present invention also relates to a method for obtaining a biosurfactant, as well as to a device for implementing this method.
The present invention finds in particular applications in the production of biopesticides or biosurfactants for the plant health industry, and also in the fields of the food, cosmetics, chemical, pharmaceutical and oil industries and the environment.
In the following description, the references between ([ ]) refer to the list of references presented at the end of the examples.
Prior Art
The conventional agricultural production system uses plant-health products of the pesticide type in order to ensure sufficient production in terms of quantity and quality, in accordance with the expectations of the markets and at a cost acceptable to the consumer. Though the use of these products affords benefits for the agricultural systems, it may nevertheless give rise to negative effects for human health and for the environment. Degradation of the quality of subterranean water and surface water and reduction in biodiversity in the agricultural environment are the consequences most frequently cited.
Biosurfactants, in particular of bacterial origin, are known to have numerous interesting properties, in particular surfactant, antiviral, antibacterial and antifungal properties able to be exploited in the plant-health field. These biosurfactants can be used alone or in a mixture of several biosurfactants. Synergetic effects have been shown when the biosurfactants are used in the form of mixtures (Ongena and Jacques, 2008 Bacillus lipopeptides: versatile weapons for plant disease biocontrol. Trends Microbiol. 16, 115-125 [1]; CZ20011620 [2]; DE 102005050123 [3]).
These biosurfactants have better biodegradability, lower toxicity and greater physicochemical resistance compared with a pesticide of chemical origin. Moreover, the cosmetic market has a particular stake in molecules of biological origin, which combine antimicrobial activities and physicochemical properties such as emulsifiers.
Biosurfactants are also used in the assisted recovery of oil contained in deposits, where the injection of biosurfactants reduces the viscosity of the oil and substantially improves the proportion of oil recovered. They are also used for combatting the pollution of water by hydrocarbons and are much more effective than chemical surfactants. Furthermore, these biosurfactants are not toxic for the ecosystem of the water treated.
The demand for biosurfactants has therefore increased over the past few years, in particular in the food, cosmetics, chemical, pharmaceutical and oil industries and the environment. Many production methods have been studied and used and have been the subject of publications or patent application filings (FR 2578552 [4]).
However, the biosurfactants currently available are not very effective and have limited biological and/or chemical properties.
There therefore exists a real need to provide alternative biosurfactants, preferably having improved properties compared with the biosurfactants of the prior art.
Moreover, there currently exists a real need to have available effective means for obtaining biosurfactants.
The methods for producing biosurfactants produced by Bacillus sp. have been particularly studied. However, these methods lead to the formation of foam caused by the addition of oxygen, in the form of bubbles. A first approach is to use aerated reactors that are mechanically agitated and to continuously extract the foam caused by the biosurfactant and containing the latter. This method is laborious and not very open to use, in particular on a large scale (Guez et al., 2007. Setting up and modelling of overflowing fed-batch cultures of Bacillus subtilis for the production and continuous removal of lipoeptides. J Biotechnol, 131, 67-75 ([5]).
In order to avoid this problem of foam, attempts have been made to work under anaerobic conditions and to use nitrate as the final electron acceptor (Davis, Lynch and Varley. 1999. The production of surfactin in batch culture by Bacillus subtilis ATCC 21332 is strongly influenced by the conditions of nitrogen metabolism. Enzyme Microb. Technol. 25, 322-329. [6]; WO 0226961 [7]; EP 1320595 [8]). Productions of biosurfactants depend greatly on the ability of the strains to adapt or not to these anaerobic conditions. No effective solution making it possible to produce biosurfactants in industrial quantities has been developed up to the present time. Moreover, the use of pesticides of chemical origin being more and more contested, it is necessary to research and use molecules of biological origin in order to replace pesticides of chemical origin and to develop methods for producing these molecules of biologic origin on an industrial scale.
There therefore exist real requirements to develop a method and device overcoming these defects, drawbacks and obstacles of the prior art, including a method for continuously producing biosurfactants in large quantities with low production costs.